Description: The Airborne Standoff Radar (ASTOR) program was launched by the United Kingdom's Ministry of Defence (MoD) to provide day/night, all-weather imagery of the ground over a large area. The intelligence imagery should be analyzed on board the aircraft and passed in near real-time to ground stations and other military systems.

The ASTOR airborne platform was designated the Sentinel R MK1. Its key system is a dual mode, long-range radar capable of delivering both Synthetic Aperture Radar (SAR) imagery and Moving Target Indicator (MTI) data. The critical information provided by this surveillance system can be transmitted to ground-based stations via data-link in support of brigade and division level operations.

The first ASTOR airborne platform, a modified Bombardier Global Express twin-engine jet aircraft, is expected to be delivered to the Royal Air Force (RAF) after 2005 achieving an Initial Operational Capability (IOC) by 2006. As of June 2005, the ASTOR equipped with dual mode radar first flight was expected in September 2005. The RAF plans call to deploy up to 5 ASTOR aircraft before 2010. As of 2014 the RAF is planning to retire the Sentinel fleet by 2015 or 2018 due to budget cuts.